British Airways has New York JFK to Amsterdam tickets at $502 to $509 round trip for peak summer travel June-August. SkyTeam and Star Alliance are in $600s and $700s.
Google Flights shows dates throughout the summer for $485 with American Airlines tickets, however, I could not price any tickets at $485 on AA website for summer dates. British Airways flights are still available at $502 to $509 for summer travel.
Google Flights New York City JFK – Amsterdam $502-$510 British Airways June-July 2017
British Airways New York JFK – London LHR – Amsterdam AMS – London LGW – New York JFK